It is planned to study the cell-mediated immune response of rats to infection with Nippostrongylus brasiliensis. The incorporation of 3H- thymidine incorporation by worm antigen-stimulated mesenteric lymph node cells will be examined, as well as the direct effect of lymphocyte from infected and control animals on larvae and worms maintained in tissue culture. The effect of lymphokines on larvae and worms will also be examined. It is proposed to test whether the mouse-adapted strain of N. brasiliensis will potentiate an ongoing IgE antibody response in the mouse. Attempts will be made to assess the contribution of T- and B- cells to the potentiated IgE response of mice. It is planned to characterize the IgA antibody response of rats to repeated intraperitoneal injections of antigen. This route of immunization has yielded the first positive IgA antibody responses observed in Sprague Dawley rats. Attempts will be made to protect rats by intraperitoneal immunization with worm extracts against challenge with infective larvae and to determine whether IgA antibodies have a role in such protection.